Oxygen separators such as disclosed in U.S. Pat. No. 3,880,616, separate fluid mixtures into first and second component parts through the retention of one component in a bed of adsorption material while allowing the other components to flow therethrough. In order to provide for continuous operation, it is common practice to use two beds of adsorption material and sequentially adsorb one bed while desorbing the other bed. A first series of solenoid valves associated with the two beds allows the fluid mixture to freely flow to a first of the two beds where one component is retained and a product effluent allowed to flow to a storage container through a conduit. At the same time a portion of the product effluent enters a second of the two beds and purges the same of the one component previously retained therein. After a period of time, a signal from a timing mechanism deactivates the first series of solenoid valves and activates a second series of solenoid valves to reverse the communication of the fluid mixture from the first of the two beds to the second. The first bed of adsorption material previously producing the product effluent is now purged by a portion of the product effluent produced in the second bed.
Theoretically, the volume of fluid mixture passing through the first and second beds of adsorption material should be equal. However in practice it has been observed that the beds of adsorption materials are nearly always different. This difference can be the result of minute changes in size betwen the beds, variations in the density of the beds, and variations in the quality of the beds such as porosity and mositure content. In addition, a few seconds change in the operation of the solenoid by the timing mechanism can cause a degradation of the beds.
Thus, one of the two beds is always producing more of a product effluent than the other. The overproducing bed experiences a component breakthrough which dilutes the product effluent during its adsorption part of the operational cycle while the underproducing bed has an excessive amount of the component retained therein at the initiation of its adsorption cycle. The underproducing bed never reaches its output potential since the adsorption cycle is terminated before the product effluent output peaks.
One method of providing identical beds requires the testing of the adsorption capacity of the beds as they are produced and thereafter selecting matching beds of the same capacity for each unit. Unfortunately, this type of production does not lend itself for rapidmanufacturing production.
Another method of acquiring optimum output from an oxygen separator requires the use of an electrical timer whereby the operation of the solenoid valve can be varied to match the adsorption capacity of the beds. The cycle of adsorption of the underproducing bed is lengthened while the cycle of adsorption of the overproducing bed is shortened until both beds are operating at top efficiency. However, this solution is only temporary since after an extended period of time the beds become unbalanced in the opposite direction since the retained component is not completely purged from the one bed.